The US Air Force's plan for testing and evaluating the Boeing KC-46A tanker is "not executable" and could overrun the schedule by at least eight months, the US military's top weapons tester said in a new report.

Michael Gilmore, director of the office of test and evaluation for the Department of Defense, sharply criticized the USAF's ability to certify the KC-46A for military operations by the end of Fiscal 2017.

USAF and Boeing officials were not immediately available to comment on Gilmore's report.

Gilmore rejects the USAF's apparent planning assumption that the KC-46A schedule can be more aggressive than most military aircraft programmes.

The USAF assumption is flawed even though the KC-46A is based on the 767-2C, a new derivative of the certified commercial airliner, Gilmore said.

Gilmore cited the US Navy's experience with the Boeing P-8A Poseidon, a submarine-hunting variant of the commercial 737-800 fuselage. Like other fixed-wing military transports, each aircraft in the P-8A test fleet averages fewer than 30 flight hours per month, Gilmore said. The USAF schedule however, schedule requires each KC-46A to average 42h per month during flight-testing.

The KC-46A also built in an "optimistic" re-fly rate of 15%, meaning the number of tests that have to be repeated due to unexpected results, Gilmore said. The P-8A refly rate is averaging 45%, he noted.

The USAF also allocated 750h to the operational test programme, but Gilmore estimates the minimum necessary to complete the schedule is 1,250h of flight tests.

If the KC-46A flight test programme achieves no worse than the P-8A's average, the schedule could be delayed a minimum of eight months, Gilmore wrote.

The USAF selected Boeing's proposal last year over an EADS North America bid. Boeing is expected to build 179 KC-46As to begin replacing the USAF's aging fleet of KC-135 tankers.

The KC-46A integrates a new refueling boom, wing-mounted refueling pods and a new cockpit system.

Source: Flight International